As MOSFETs are scaled into sub 100 nm (decanano) dimensions, quantum mechanical confinement and tunnelling start to dramatically affect their characteristics. In this paper we describe the introduction of quantum corrections within a 3D drift diffusion simulation framework using quantum potentials. We compare the density gradient (DG) and the effective potential (EP) approaches in term of accuracy and computational efficiency. Their application is illustrated with examples of 3D statistical simulations of intrinsic fluctuation effects in decanano MOSFETs. We also speculate about the capability of the DG formalism to handle source-to-drain tunnelling in sub 10 nm (nano) MOSFETS.